In my previously filed co-pending application, Ser. No. 520,742, filed Nov. 4, 1974, now U.S. Pat. No. 4,035,762, issued July 12, 1977, incorporated herein by reference, I discussed the desirability of providing relatively simple means for measuring a position along a line, either straight or curved, or on a plane or other curvilinear surface, with a high degree of accuracy at a reasonable cost. Such application discussed various techniques of the prior art for performing such position determinations and further described a variety of inventive techniques for providing such position determinations which techniques represented improvements over the prior art discussed therein.
The embodiments described therein require two relatively movable members. In a particular embodiment, for example, one member may comprise a driver transducer and a delay line both fixedly positioned and a second member may comprise a receiver transducer which is movable with respect to the fixed driver transducer and delay line. In such an embodiment, power is required to be supplied to both members so that suitable brushes are required for such purposes. Further, the resolution of the displacement measurement depends upon the phase shift experienced by a continuous elastic wave traveling once along a single delay line element in one direction only parallel to the distance to be measured.
It is desirable to provide a position sensing device in which power is not required to be supplied to both members (so that the need for brushes can be eliminated) and in which the resolution is improved over that of the previously described devices.